/*
* Licensed to Elasticsearch under one or more contributor
* license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright
* ownership. Elasticsearch licenses this file to you under
* the Apache License, Version 2.0 (the "License"); you may
* not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
package org.elasticsearch.script.mustache;
import com.github.mustachejava.Mustache;
import org.elasticsearch.common.Nullable;
import org.elasticsearch.common.component.AbstractComponent;
import org.elasticsearch.common.inject.Inject;
import org.elasticsearch.common.io.FastStringReader;
import org.elasticsearch.common.io.UTF8StreamWriter;
import org.elasticsearch.common.io.stream.BytesStreamOutput;
import org.elasticsearch.common.settings.Settings;
import org.elasticsearch.script.CompiledScript;
import org.elasticsearch.script.ExecutableScript;
import org.elasticsearch.script.ScriptEngineService;
import org.elasticsearch.script.SearchScript;
import org.elasticsearch.search.lookup.SearchLookup;
import java.io.IOException;
import java.lang.ref.SoftReference;
import java.util.Collections;
import java.util.Map;
/**
* Main entry point handling template registration, compilation and
* execution.
*
* Template handling is based on Mustache. Template handling is a two step
* process: First compile the string representing the template, the resulting
* {@link Mustache} object can then be re-used for subsequent executions.
*/
public class MustacheScriptEngineService extends AbstractComponent implements ScriptEngineService {
/** Thread local UTF8StreamWriter to store template execution results in, thread local to save object creation.*/
private static ThreadLocal<SoftReference<UTF8StreamWriter>> utf8StreamWriter = new ThreadLocal<>();
/** If exists, reset and return, otherwise create, reset and return a writer.*/
private static UTF8StreamWriter utf8StreamWriter() {
SoftReference<UTF8StreamWriter> ref = utf8StreamWriter.get();
UTF8StreamWriter writer = (ref == null) ? null : ref.get();
if (writer == null) {
writer = new UTF8StreamWriter(1024 * 4);
utf8StreamWriter.set(new SoftReference<>(writer));
}
writer.reset();
return writer;
}
/**
* @param settings automatically wired by Guice.
* */
@Inject
public MustacheScriptEngineService(Settings settings) {
super(settings);
}
/**
* Compile a template string to (in this case) a Mustache object than can
* later be re-used for execution to fill in missing parameter values.
*
* @param template
* a string representing the template to compile.
* @return a compiled template object for later execution.
* */
public Object compile(String template) {
/** Factory to generate Mustache objects from. */
return (new JsonEscapingMustacheFactory()).compile(new FastStringReader(template), "query-template");
}
/**
* Execute a compiled template object (as retrieved from the compile method)
* and fill potential place holders with the variables given.
*
* @param template
* compiled template object.
* @param vars
* map of variables to use during substitution.
*
* @return the processed string with all given variables substitued.
* */
public Object execute(Object template, Map<String, Object> vars) {
BytesStreamOutput result = new BytesStreamOutput();
UTF8StreamWriter writer = utf8StreamWriter().setOutput(result);
((Mustache) template).execute(writer, vars);
try {
writer.flush();
} catch (IOException e) {
logger.error("Could not execute query template (failed to flush writer): ", e);
} finally {
try {
writer.close();
} catch (IOException e) {
logger.error("Could not execute query template (failed to close writer): ", e);
}
}
return result.bytes();
}
@Override
public String[] types() {
return new String[] {"mustache"};
}
@Override
public String[] extensions() {
return new String[] {"mustache"};
}
@Override
public boolean sandboxed() {
return true;
}
@Override
public ExecutableScript executable(Object mustache,
@Nullable Map<String, Object> vars) {
return new MustacheExecutableScript((Mustache) mustache, vars);
}
@Override
public SearchScript search(Object compiledScript, SearchLookup lookup,
@Nullable Map<String, Object> vars) {
throw new UnsupportedOperationException();
}
@Override
public Object unwrap(Object value) {
return value;
}
@Override
public void close() {
// Nothing to do here
}
@Override
public void scriptRemoved(CompiledScript script) {
// Nothing to do here
}
/**
* Used at query execution time by script service in order to execute a query template.
* */
private class MustacheExecutableScript implements ExecutableScript {
/** Compiled template object. */
private Mustache mustache;
/** Parameters to fill above object with. */
private Map<String, Object> vars;
/**
* @param mustache the compiled template object
* @param vars the parameters to fill above object with
**/
public MustacheExecutableScript(Mustache mustache,
Map<String, Object> vars) {
this.mustache = mustache;
this.vars = vars == null ? Collections.EMPTY_MAP : vars;
}
@Override
public void setNextVar(String name, Object value) {
this.vars.put(name, value);
}
@Override
public Object run() {
BytesStreamOutput result = new BytesStreamOutput();
UTF8StreamWriter writer = utf8StreamWriter().setOutput(result);
((Mustache) mustache).execute(writer, vars);
try {
writer.flush();
} catch (IOException e) {
logger.error("Could not execute query template (failed to flush writer): ", e);
} finally {
try {
writer.close();
} catch (IOException e) {
logger.error("Could not execute query template (failed to close writer): ", e);
}
}
return result.bytes();
}
@Override
public Object unwrap(Object value) {
return value;
}
}
}